<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <pre>
        &lt; script type="text/javascript"> 
            var i = iResult = 0;
            function sum()
            {
               for (var i = 0; i  arguments.length; i++)
               {
                  iResult += arguments[i];
               }
                return iResult;
            }
            //应用
            alert(sum(1,2,3,4,5,6,7,8,9,10));  //输出55
     &lt; /script>
 </pre>

    <button>结果</button>


</body>
<script>
    var btn = document.querySelector("button")
    console.log(btn)
    var i = iResult = 0
    btn.onclick=function(){
        console.log(111)
         this.innerHTML=sum(1,2,3) //调用
    }
    
    //封装一个函数
    function sum(){
         for(var i=0;i<arguments.length;i++){
             iResult+=arguments[i] 
         }
         return iResult
    }
    

</script>

</html>